Control of the Activated Sludge Treatment Process, 1998 Environmental Conference Proceedings

G. Sedgwick, Alberta Research Council

D. Moore, Alberta Newsprint Company

W. Lyka, Millar Western Pulp Ltd.

R. Denton, Slave Lake Pulp Corporation

The activated sludge process provides effective treatment of pulp mill effluent. The process is prone to upsets owever, particularly in situations where there is wide variation in the pulping process. This paper presents the esults of a multi-mill project aimed at upset-free control of the treatment process. The project covers three aspects: rocess control software development, on-line instrumentation testing and computer simulation of process behavior.

Advisory control software has been developed and is operating in all three mills. The control package is a rule-based ystem which monitors all treatment system variables, analyses the data using customized rules, and makes ontrol recommendations to the treatment system operators. The package runs on a windows-based PC networked to the mill-wide information system for process updates. The control software has a number of features. A summary screen provides the status of a suite of critical process variables. If anomalies are detected, operator selectable screens provide detail on recommendations, background reasoning, and trending of variables. The control improvements and operating experience of the three mills are summarized. Stable control has required the installation of on-line instrumentation to provide accurate measurements of treatment system variables. This was accomplished by extensive mill-site testing and verification of selected instruments.

Equipment has been evaluated for the on-line measurement of DO, ammonia and phosphate nutrients, sludge blanket levels and most recently for on-line respirometry. The diagnosis of process dynamics through on-line respirometric measurements and computer simulation has provided process insight and control information. The results of the testing programs are presented.